Week13 - Home - Clark Science CenterExercise • Write a program that reads the ﬁle data.txt,...

mith College

Computer Science

Dominique Thiébaut [email protected]

CSC231Week 13— Introduction to C

Fall 2019

Complete the code

shown here

Computer Science Dominique Thiebaut

getcopy C/decrementArray.c

Exercise

Complete the code

shown here


Solution

Exercise


• Write a C program that uses functions to find the largest integer in A. The result is passed back using a return statement.

Solutiongetcopy C/findMaxUsingFunctionSol.c


Exercise

• Write another program that does the same thing but the max is passed back by reference.


Solutiongetcopy C/findMaxUsingFunction2sol.c


Input/OutputIO

Input From User


(cont’d)

a.outEnter your name, please: MickeyEnter your age: 21Enter your version of pi: 3.14159Mickey is 21 years old, and thinks pi is 3.1415901184


Dynamic Variables


• Dynamic: think "new" in Java

• malloc() = Memore Allocation for new data structure


RAM


user

pro

g

malloc()

user

pro

g

malloc()

RAM


OperatingSystem

RAM


OperatingSystem

dyn

user

pro

g

malloc()

RAM


OperatingSystem

dyn

(void*) p

user

pro

g

malloc()

RAM


OperatingSystem

dyn

(void*) p

p

user

pro

g

malloc()


getcopy C/malloc1.c

Malloc

Exercise• Modify the previous program that computed the

max of an array, but this time you allocate the array dynamically, with numbers provided by the user.


Solution


getcopy C/findMaxUsingFunction3sol.c

sizeof()can be tricky…


sizeof ()


sizeof(A) = 20sizeof(A[0]) = 4sizeof(B) = 8sizeof(B[0]) = 4sizeof(p) = 8sizeof(*p) = 4sizeof(name) = 14strlen(name) = 13sizeof(a) = 4sizeof(x) = 4

sizeof ()


sizeof(A) = 20sizeof(A[0]) = 4sizeof(B) = 8sizeof(B[0]) = 4sizeof(p) = 8sizeof(*p) = 4sizeof(name) = 14strlen(name) = 13sizeof(a) = 4sizeof(x) = 4

Different!

sizeof ()


File IO

File I/O: Output


C/fileIOOutput.c

File I/O: Input


C/fileIOInput.c


File I/O: Reading Ints [~handout] cat fileOfInts.txt 41 2 34 5 67 8 910 11 12


File I/O: Reading Ints

C/fileIOReadNumbers.c


[~handout] gcc fileIOReadNumbers.c[~handout] a.out1, 2, 34, 5, 67, 8, 910, 11, 12

File I/O: Reading Ints

Exercise• Write a program that reads the file data.txt, which

has the number of ints it contains on the first line, then one int per line for the rest of the file. Your program must use a dynamic array to store the numbers, and find the max of the array, and print it.


Function Prototypes

and Multi-File Projects


Original


myfuncs.c

smallestLargestSum3.c


myfuncs.h


Summary• C has a lot in common with Java

• C programmers must know how to use memory (malloc, pointers)

• No garbage collector: free dynamic structures yourself!

• Explicitly pass arguments by value or by reference to functions


D. Thiebaut, Computer Science, Smith College

End of Video Lecturehttps://www.youtube.com/watch?v=LFpoUFIfV0M&a=youtu.be

https://www.youtube.com/watch?v=LFpoUFIfV0M&a=youtu.be


Logistics and Update

• Video lecture for Monday's snow day + Quiz

• No office hours today

• Office hours tomorrow (12/5) 12-1 p.m.

• Homework extended to 12/5 11:55 p.m.

• Homework 11 (optional) released tomorrow morning


And now, something completely different…

Executablegcc addition.c


And now, something completely different…

Executablegcc addition.c

gcc -S -m32 -masm=intel addition.c


ReviewMalloc


ReviewMalloc

Linked-Listsin C



Outline

• Linked Lists in C

• Structures in C

• Creating a Node

• Adding a Node

• Removing a Node

‘Alpha’

‘Zero’

‘Beta’

‘Apple’

head

"Alpha"

"Zero"

"Beta"

"Apple"

head



NULL

((void *)0)

"Alpha"

"Zero"

"Beta"

"Apple"

head

The Node in C"Alpha"


http://www.gnu.org/software/gnu-c-manual/gnu-c-manual.html#Structures

C Structs

• Early attempt at encapsulating data

• Members are accessed using the dot notation:




Struct Example


Struct Example


Struct Example


getcopy C/structExample.c

The Head of the List


head

The Head of the List


head

That’s anempty list!

Displaying the List


"Alpha" "Zero" "Apple"

head

"Beta"

Creating the List


"Apple"

head

"Beta"




getcopy C/linkedListStrings.c

Exercise

• Add code to the linkedListStrings.c program that will remove all the nodes from the list, one by one (and free them).

• Make your code display the list after each deletion


Exercise

• Use functions for adding and removing nodes…


Main ProgramCalling

Functions

Solution


getcopy C/linkedListStrings2.c


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Week13 - Home - Clark Science CenterExercise • Write a program that reads the ﬁle data.txt,...

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